import collections
import datetime

from django.db import models
from django.db.models import Q

import reversion

import groups.models

# Create your models here.

class Space(models.Model):
    number = models.CharField(max_length=20, unique=True, )
    asa_owned = models.BooleanField(default=True, )
    notes = models.TextField(blank=True, )

    def __unicode__(self, ):
        if self.asa_owned:
            asa_str = "ASA"
        else:
            asa_str = "Non-ASA"
        return u"%s (%s)" % (self.number, asa_str)

    def build_access(self, time=None, group=None, ):
        """Assemble a list of who had access to this Space.

        time:
            optional; indicate that you want access as of a particular time.
            If omitted, uses the present.
        group:
            optional; indicates that you want access via a particular group.
            If omitted, finds access via any group.

        Return value:
            tuple (access, assignments, aces, errors)
            access is the main field that matters, but the others are potentially useful supplementary information

            access:
                Group.pk -> (ID -> Set name)
                Indicates who has access. Grouped by group and ID number.
                Usually, the sets will each have one member, but ID 999999999 is decently likely to have several.
                The SpaceAccessListEntrys will be filtered to reflect assignments as of that time.
            assignments:
                [SpaceAssignment]
                QuerySet of all SpaceAssignments involving the space and group at the time
            aces:
                [SpaceAccessListEntry]
                QuerySet of all SpaceAccessListEntrys involving the space and group at the time.
                This is not filtered for the ace's group having a relevant SpaceAssignment.
            errors:
                [String]
                errors/warnings that occurred.
                Includes messages about groups no longer having access.
        """

        if time is None:
            time = datetime.datetime.now()
        errors = []
        time_q = Q(end__gte=time, start__lte=time)
        assignments = SpaceAssignment.objects.filter(time_q, space=self)
        aces = SpaceAccessListEntry.objects.filter(time_q, space=self)
        if group:
            assignments = assignments.filter(group=group)
            aces = aces.filter(group=group)
        access = {}    # Group.pk -> (ID -> Set name)
        for assignment in assignments:
            if assignment.group.pk not in access:
                access[assignment.group.pk] = collections.defaultdict(set)
        for ace in aces:
            if ace.group.pk in access:
                access[ace.group.pk][ace.card_number].add(ace.name)
            else:
                # This group appears to no longer have access...
                errors.append("Group %s no longer has access to %s, but has live ACEs." % (ace.group, self, ))
        return access, assignments, aces, errors

reversion.register(Space)


class CurrentAssignmentManager(models.Manager):
    def get_query_set(self, ):
        return super(CurrentAssignmentManager, self).get_query_set().filter(
            start__lte=datetime.date.today,
            end__gte=datetime.date.today,
        )

class SpaceAssignment(models.Model):
    END_NEVER       = datetime.datetime.max

    group = models.ForeignKey(groups.models.Group)
    space = models.ForeignKey(Space)
    start = models.DateField(default=datetime.datetime.now)
    end = models.DateField(default=END_NEVER)

    notes = models.TextField(blank=True, )
    locker_num = models.CharField(max_length=10, blank=True, help_text='Locker number. If set, will use the "locker-access" OfficerRole to maintain access. If unset/blank, uses "office-access" and SpaceAccessListEntry for access.')

    objects = models.Manager()
    current = CurrentAssignmentManager()

    def expire(self, ):
        self.end_time = datetime.datetime.now()-self.EXPIRE_OFFSET
        self.save()

    def is_locker(self, ):
        return bool(self.locker_num)

    def __unicode__(self, ):
        return u"<SpaceAssignment group=%s space=%s locker=%s start=%s end=%s>" % (
            self.group,
            self.space,
            self.locker_num,
            self.start,
            self.end,
        )


class CurrentACLEntryManager(models.Manager):
    def get_query_set(self, ):
        return super(CurrentACLEntryManager, self).get_query_set().filter(
            start__lte=datetime.datetime.now,
            end__gte=datetime.datetime.now,
        )

class SpaceAccessListEntry(models.Model):
    END_NEVER       = datetime.datetime.max

    group = models.ForeignKey(groups.models.Group)
    space = models.ForeignKey(Space)
    start = models.DateTimeField(default=datetime.datetime.now)
    end = models.DateTimeField(default=END_NEVER)

    name = models.CharField(max_length=50)
    card_number = models.CharField(max_length=20)

    objects = models.Manager()
    current = CurrentACLEntryManager()

    def expire(self, ):
        self.end_time = datetime.datetime.now()-self.EXPIRE_OFFSET
        self.save()

    def format_name(self, ):
        return u"%s (%s)" % (self.name, self.card_number, )

    def __unicode__(self, ):
        return u"<SpaceAccessListEntry group=%s space=%s name=%s start=%s end=%s>" % (
            self.group,
            self.space,
            self.name,
            self.start,
            self.end,
        )